Electric circuit interrupter



Aug. 3,1937. H. BURMEISTER ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 28, 1957 Ihventcw". Hev'mcrn'n Buv'mels cerr,

- is Attorheg.

Patented Aug; 3, 1937 UNH'ED STATEfi PAT r OFFiCE attach anaemic omeurr mrcanorrua Application January 2 8, 1937, Serial No. 122,774 In Germany February 111, 1936 8 Claims.

formed by decomposition of a material by the are 5 upon opening of the circuit is utilized to interrupt the arc.

In a. well-known formoi' circuit interrupter of the aforesaid type, the arc is drawn in a narrowchannel or tube composed of material which, under the influence of the heat of the arc, emits gases or vapors tending to extinguish the arc. Inorganic materials, such as for example, boric acid, ammonium alum, etc., have been proposed as the gas-emitting material. In these substances water is chemically combined so that under the influence of the are vapors are released for the arc-extinguishing process. These vapors producing inorganic materials cannot, however, be molded or formed satisfactorily for circuit interruptingservice since they lack themore desirable mechanical characteristics such as strength and rigidity, which are necessary in connection with the explosive pressures developed during interruption of the circuit.

For these reasons, organic materials, such as hard rubber, paper, or other fibrous materials, whichunder the influence of the are, also evaporate so as to emit an arc-extinguishing gas and also serve as a deflecting insulating service, are preferable. Moreover, these organic or fibrous materials have the advantage that they can easily be formed in tubular and other shapes and have inherently high mechanical strength.

There are, however, certain disadvantages in the use of circuit interrupter tubes composed of organic materials since to a great extent decomposition by the heat of the are results in a reduction to carbon. Since the carbon formation may result in a film of soot along the insulating sur face of the circuit interrupter, the interrupting process, particularly in the case of high voltages, may be accompanied by fiashover by reason of the conducting path formed by the carbon.

In accordance with the present invention, organic materials, such as linen, paper, wool, etc., can be used in combination with impregnating materials, such as fluid artificial resin. With a sufficient amount of impregnating material and or sealed by the impregnating material so that a. soot formation is avoided.

My invention will be more fully set forth in 5 the following description referring to the accom panying drawing, and the features of-novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing the single figure thereof is an elevational view partly in section of an electric circuit breaker of the expulsion type to which the present invention is applicable. There is shown merely by way of example an electric circuit interrupter, more particularly, a circuit breaker having means, such as the stationary contact, 5 and the movable rod contact 2, for opening the circuit so as to form an arc, and an insulating structure 3 forming an arc chamber for closely confining the are between the contacts. The insulating structure 3 consists of a tubular member closed at the fixed contact end and open at the other end for receivingthe rod contact. Upon opening of the circuit separation of the contacts and 2 causes formation of an arc which decomposes some of the material of the arc chamber walls 3. The gas so formed is under considerable pressure by reason of the comparatively close fit of the rod contact 2 in the fib er tube 3 with the result that when the rod leaves the tube a. blast of gas is released as indicated for interrupting the are.

In accordance with the present invention the fluid artificial resin, when used as a means of impregnation may consist of a carbamide (amino plastic mass). In these materials nitrogen is chemically combined so that in the circuit interrupting process this gas is released by the arc. The carriermaterial on the other hand, in so far as it comes into contact with the arc burns practically without residue so that the operation of the circuit interrupter is not hindered by the Soot formation.

It has also been found that a further increase in the interrupting effect and also a greater freedom in the selection of the carrier materials without taking into account their soot forming characteristics, can be obtained if an appreciable admixture of carbonate, preferably an ammonium carbonate is added to the impregnating material. Apparently in the arc-extinguishing proc-. ess, the carbonate acts as a garrier of oxygen which converts the carbon produced in the switch tubeunder the influence of the are heat into carbon monoxide or carbon dioxide respectively.

Thus, on the one hand'a very eifective arcinterrupting gas, namely carbonic acid, is produced, and on the other hand a soot formation is avoided by the combination of the carbon with oxygen produced by dissociation oi the carbonate by the arc.

In lieu of ammonium carbonate (NI-1400s), there can also be used some carbonates wherein the hydrogen of the ammonium is totally or partially replaced by aliphatic or aromatic compounds. For example, tetraethyl ammonium carbonate, (N(C:Hs)4) 200:, can be used in place of the ammonium carbonate or ammonium bi carbonate. The advantage of these salts lies in the larger quantity oi. gas that can be produced, and especially in the larger hydrogen content. In regard to the latter. the carbonates oi monomethylamine are particularly outstanding.

The admixture, in accordance with the invention of a carbonate-to organic materials serving as gas producing materials for arc interrupting tubes 0! the character above discussed also makes possible the use or the good arc-extinguishing properties of hard rubber. Following this method, a material is produced which,

surprisingly, does not tend toward sootformation even under comparatively long exposure to arcing, and which has a greater arc-extinguishing efiect.

As an example of an admixture to hard rubber, calcium bicarbonate, calcium carbonateor magnesium carbonate can be used. These materials are suitably added to the rubber in the vulcaniz:

ing process as a filling material. Further examples oi filling materials include other carbonates, such as marble dust or chalk. A satisfactory final product can be obtained by volumetric mixture of 50 per cent (caoutchouc+sulphur) and 50 per cent marble dust. I! desired, boric acid can also be used in place of part oi! the filling material.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: v

1. An electric circuit interrupter comprising means for opening the circuit so as to form an arc, and an insulating structure disposed adjacent and in confining relation to said arc, said insulating structure comprising a mechanically strong organic material impregnated with an inaoaaom.

organic material which upon ticcompcsitiuu iii)" said are yields an arc-interrupting gas.

2. An electric circuit interrupter comprising means for opening the circuit so as to term. an arc, and an insulating structure disposed adju cent and in confining relation to said are, said structure consisting of a mechanically strong organic material impregnated with a substantially equal or greater amount 0! an inorganic material which upon'decomposition by said are yields an arc-interrupting gas including carbon dioxide.

3. An electric circuit interrupter comprising means for opening the circuit so as to term an arc,'and an insulating structure disposed adjacent and in confining relation to said arc, said structure consisting oi a mechanically strong or ganic carrier material impregnated with an inorganic material including a carbonate so that said structure when subjected to said are yields carbon dioxide gas for interrupting said arc.

4. An electric circuit interrupter comprising means for opening the circuit so as to form an arc, and an insulating. structure disposed addscent and in confining relation to said arc, said structure consisting of a mechanically strong fibrous material impregnated with ammonium bicarbonate.

means for opening the circuit so as to form an arc, and an insulating structure disposed adjacent and in confining relationto said arc, said structure consisting 01' an organic fibrous material impregnated with a carbonate in which hydrogen 0! an ammonium radical in chemical combination therewith is replaced wholly or partly by an organic compound.

6. An electric circuit interrupter including an \arc-conilning structure, said structure consisting of hard rubber impregnated with a carbonate adapted to be decomposed by the heat of the are for yielding snare-extinguishing gas.

'7. An electric circuit interrupter including an arc-confining structure, said structure consisting of hard rubber impregnated with calcium carbonate in approximately equal quantities by volume.

8. An electric circuit interrupter including an arc-confining structure, said structure consisting of an approximately equal mixture by volume of hard rubber and marble dust.

' HERMANN B. 

